Ribonucleic acid interference (RNA interference, RNAi) refers to the following phenomenon: after double-stranded RNA (dsRNA) homologous to a certain sequence in an endogenous mRNA coding region is introduced into a cell, the mRNA undergoes specific degradation, with the result that the gene is silenced. Research has shown that double-stranded RNA of length 21-23 nt can specifically induce RNAi at the transcription or post-transcription level (Tuschl et al., Cell (2000) 101: 25-33). Tumors are major diseases that threaten human health. In spite of chemotherapy, radiotherapy, and combination therapy, the five-year survival rate for tumor patients is still quite low. New avenues in tumor treatment could be opened up if the genes relating to the onset and progress of tumors could be subjected to RNA interference. In recent years, RNAi has become an effective strategy for tumor gene therapy. The use of RNAi techniques can inhibit the expression of oncogenes, mutated tumor suppressor genes, cell cycle-related genes, and anti-apoptosis genes and thereby inhibit the occurrence and development of tumors (Uprichard, FEBS Lett. (2005) 579:5996-6007).
The zinc finger protein family is the largest protein family in human and is the most common structural element in nucleic acid identification. Research has found that 1% of human genes belong to the zinc finger protein gene family. Zinc finger proteins can regulate gene expression by targeting gene promoter regions, and play an important role in the growth, proliferation, and differentiation of histocytes. Their abnormal expression may cause many diseases, including malignant tumors (Yajima et al., J Dermatol Sci. (2009) 55:68-70; Oyanagi et al., Lung Cancer (2004) 46:21-28; Witkiewicz-Kucharczyk & Bal, Toxicol. Lett. (2006) 162:29-42; Vendrell et al., Oncogene (2007) 26:4656-4667).
The ZFY (zinc finger-Y) gene family is a highly conserved gene family among vertebrates. It is now known that the ZFY gene family includes three members: the ZFX, ZFY, and ZFA genes. Their molecular structures are highly similar (North et al., Nucleic Acids Res. (1991) 19:2579-2586). Generally, all mammals have ZFX and ZFY genes, with the ZFX gene being located on the X chromosome and the ZFY gene being located on the Y chromosome (Palmer et al., Proc. Natl. Acad. Sci. USA (1990) 87:1681-1685). Extensive research has verified that the ZFY gene family is related to the sex-determination of animals. In-depth studies have shown that the ZFY gene family may be related to testicular development and may decide the sexual development of animals (Schneider-Gadicke et al., Cell (1989) 57:1247-1258).
The full-length ZFX protein contains an acidic transcriptional activation domain (AD), a nuclear localization sequence (NLS), and a DNA binding domain (DBD) with 13 Cys2His2 (C2H2) zinc finger structures (Poloumienko et al., Genome (2004) 47: 74-83). In mammalian cells, the C2H2 zinc finger structure is one of the most common protein structures and has a potential transcription-regulation function. So far, more than 800 proteins have been found to have such a zinc finger structure, and the majority has been verified as having important physiological functions. In recent years, scientists have discovered, in the course of researching the gene expression processes of different stem cells, that the ZFX gene is highly expressed within several types of stem cells (Ramalho-Santos et al., Science (2002) 298:597-600). It has also been reported that the ZFX gene has the function of regulating stem cell self-renewal (Cellot & Sauvageau, Cell (2007) 129:239-241). However, there have been no reports so far on the ZFX gene in tumor-related fields.